Trial is an essential part of the new mold before injection molding or when the machine is replaced with other molds. The results of the test results will directly affect whether the subsequent production of the factory is smooth. Therefore, it is necessary to follow reasonable operation steps and record the useful technical parameters in the trial process during the trial molding process to facilitate mass production of the product.
Precautions before the test
1. Understand the relevant information of the mold:
It is best to get the design drawing of the mold, analyze it in detail, and get the mold technician to participate in the test work.
2. First check the mechanical coordination action on the workbench:
Pay attention to whether there are any scratches, missing parts and looseness, whether the mold-to-slide action is correct, whether there is leakage in the water channel and the air pipe joint, and if the opening of the mold is limited, it should be marked on the mold. If the above actions can be done before hanging the mold, it is possible to avoid the problem of finding the problem when hanging the mold, and then the waste of work caused by disassembling the mold.
3. When it is determined that the various parts of the mold are suitable for movement, it is necessary to select a suitable test injection machine. When selecting, you should pay attention to:
(a) What is the maximum injection volume of the injection molding machine?
(b) Whether the inner distance of the tie rod is placed under the mold
(c) Whether the maximum moving itinerary of the activity template meets the requirements
(d) Are other related test tools and accessories ready?
After everything is confirmed to be no problem, the next step is to hang the mold. When hanging, pay attention to all the clamp templates and the hanging fishing before the mold is opened, so as not to loosen or break the clamp template, so that the mold falls. After the mold is installed, the mechanical action of each part of the mold should be carefully checked, such as the action of the skateboard, the thimble, the retracting structure and the limit switch. Also pay attention to whether the nozzle and the feed port are aligned. The next step is to pay attention to the mold clamping action. At this time, the mold closing pressure should be lowered. In the manual and low speed clamping movements, pay attention to whether there is any smooth movement and abnormal sound. The process of lifting the mold is actually relatively simple. It is difficult to focus on the center of the mold gate and the nozzle. It is usually possible to adjust the center by means of test paper.
4. Increase the mold temperature:
According to the performance of the raw materials used in the finished product and the size of the mold, an appropriate mold temperature control machine is used to raise the temperature of the mold to the temperature required for production. After the mold temperature is increased, the movement of each part must be reviewed again, because the steel may cause jamming after thermal expansion, so it is necessary to pay attention to the sliding of each part to avoid the occurrence of strain and chatter.
5. If the experimental plan rule is not implemented in the factory, we recommend that only one condition can be adjusted at a time when adjusting the test conditions to distinguish the impact of a single condition change on the finished product.
6. Depending on the raw materials, make a proper baking of the original used.
7. Try and use the same raw materials as much as possible in future mass production.
8. Do not try the test by default. If there is any color requirement, you can arrange the test color together.
9. Internal stress and other problems often affect the secondary processing. After the test is finished, the finished product is stabilized and the secondary processing die is placed at a slow speed. After the mold is closed, the mold pressure should be adjusted and the movement should be repeated several times to check whether there is any joint. The mold pressure is uneven, so as to avoid burrs and mold deformation of the finished product.
After the above steps are checked, the mold closing speed and the closing pressure are lowered, and the safety buckle and the ejection stroke are set, and then the normal closing mode and the closing speed are adjusted. If the limit switch involving the maximum stroke is involved, the mold opening stroke should be adjusted slightly shorter, and the high speed mold opening action should be cut off before the maximum stroke of the mold opening. This is because during the entire mold opening stroke during the mold clamping, the high speed stroke is longer than the low speed. The mechanical ejector rod on the plastic machine must also be adjusted after the full-speed mold opening action to prevent the ejector plate or the peeling plate from being deformed by force.
Please check the following items before making the first shot:
(a) Whether the feeding schedule is too long or insufficient.
(b) Whether the pressure is too high or too low.
(c) Whether the filling speed is too fast or too slow.
(d) Whether the processing cycle is too long or too short.
To prevent short shots, breakage, deformation, burrs and even damage to the mold.
If the processing cycle is too short, the thimble will pierce the finished product or strip the finished product. This type of situation may take you two or three hours to remove the finished product. If the processing cycle is too long, the weak part of the mold core may be broken due to shrinkage of the rubber. Of course, you can't predict all the problems that may occur during the trial process, but taking precautions and taking timely measures will help you avoid serious and expensive losses.
Main steps of the test
In order to avoid wasted time and trouble during mass production, it is necessary to patience to adjust and control various processing conditions, find the best temperature and pressure conditions, and develop standard test procedures, and can be used for Establish a daily working method.
1. Check whether the plastic material in the barrel is correct and whether it is baked according to the regulations. (It is possible to obtain different results if different materials are used in the test mode and production).
2. The cleaning of the material pipe should be thorough, in order to prevent the inferior compound or miscellaneous materials from being injected into the mold, because the inferior rubber and miscellaneous materials may cause the mold to be stuck. Check that the temperature of the tube and the temperature of the mold are suitable for the raw materials for processing.
3. Adjust the pressure and the amount of injection to produce a finished product with satisfactory appearance, but do not run the burrs, especially if some of the cavity products are not fully solidified. Please consider before adjusting various control conditions, because filling A slight change in the rate may cause a large change in filling.
4. Be patient and wait until the conditions of the machine and the mold are stable, that is, the medium-sized machine may have to wait for more than 30 minutes. This time can be used to see what can happen to the finished product.
5. The advancement time of the screw should not be shorter than the time when the plastic of the gate is solidified, otherwise the weight of the finished product will decrease and the performance of the finished product will be damaged. And when the mold is heated, the screw advance time also needs to be lengthened to compact the finished product.
6. Reasonable adjustment to reduce the total processing cycle.
7. Run the newly transferred conditions for at least 30 minutes to stabilize, and then at least continuously produce a dozen full-mode samples, mark the date and quantity on the holder, and place them separately according to the cavity to test the stability of the operation. And derive reasonable control tolerances. (especially valuable for multi-hole molds).
8. Measure and record the important dimensions of the continuous sample (should be re-sampled when the sample is cooled to room temperature).
9. Compare the dimensions of each model sample and note that:
(a) Whether the size of the product is stable.
(b) Whether certain sizes have an increasing or decreasing trend and indicate that machining conditions are still changing, such as poor temperature control or oil pressure control.
(c) Whether the change in size is within the tolerance range.
10. If the finished product size does not change and the processing conditions are normal, it is necessary to observe whether the quality of each finished product of each cavity is acceptable, and the size can be within the tolerance. Make a note of the number of holes that are continuous or large or smaller than the average to check if the size of the mold is correct.
Record the parameters obtained during the trial process
Record and analyze the data as a need to modify the mold and production conditions, and as a reference for future mass production.
1. Make the processing run time longer to stabilize the melt temperature and hydraulic oil temperature.
2. According to the size of all finished products is too large or too small to adjust the machine conditions, if the shrinkage rate is too large and the finished product appears to be insufficient, it can also be used to increase the gate size.
3. If the size of each cavity is too large or too small, if the dimensions of the cavity and the door are correct, then the machine conditions, such as filling rate, mold temperature and pressure of each part, should be tested, and some modes should be examined. Whether the hole is filled slowly.
4. According to the matching situation of the finished cavity products or the displacement of the mold core, the correction is made separately, and the mold filling rate and the mold temperature may be tried again to improve the uniformity.
5. Check and modify the failure of the injection machine. If the oil pump, oil valve, temperature controller, etc. are bad, the processing conditions will change. Even the perfect mold can not work well in the poorly maintained machine. After reviewing all of the recorded values, a set of samples is retained to proofread whether the corrected samples have improved.
Properly keep records of all sample inspections during the trial process, including various pressures during the processing cycle, melt and mold temperatures, tube temperature, injection time, screw feed period, etc. In short, all future contributions should be preserved. It is possible to successfully establish data on the same processing conditions in order to obtain products that meet the quality standards.
At present, the mold temperature is often neglected during the test of the factory, and the mold temperature is the most difficult to master in the short-term trial and future mass production. The incorrect mold temperature is enough to affect the sample size, luminosity, shrinkage, flow pattern and material loss. If the mold temperature controller is not used for the future mass production, it may be difficult.
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